Comment 4 for bug 587546

Tried the position_fix=1 suggestion without notable benefit. However, after that it occurred to me that I had to tweak alsa-base.conf in Karmic to get sound at all. I have now forward-ported the changes from my Karmic installation, so the relevant lines now read:

options snd slots=snd-hda-intel,snd-ens1370
options snd-hda-intel index=0
options snd_ens1370 index=1
options snd-hda-intel model=3stack-660-digout
options snd-hda-intel enable_msi=1
options snd-hda-intel position_fix=1

Since installing those changes I have observed no further problems with the sound system. If you would like to narrow down which change(s) were necessary, I can start commenting out some of the above until the problems come back. Otherwise, my problem appears to be solved and I'm happy.